Types of Drag in Helicopters
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This video's topic is covers the types of drag in helicopters. We know from basic aerodynamics that thrust and drag are opposing forces. But what exactly is drag? Drag is the force that opposes or resists the motion of an object as it travels through the air. An easy way to show this visually is to compare drag is relation to airspeed.
Drag can be briefness down into 3 types. The first one being Parasite drag. Parasite drag is probably the easiest to understand because to everything moving through the air whether it be a helicopter, plane , a car, or even you hand out of the window of a car. This type of drag is the air resistance on an object as it moves. It increases with both surface area and speed. This is why you see streamlining in high speed cars and planes. In order to achieve higher speeds, the surface area must be reduced. In relation to airspeed, parasite drag increases rapidly and exponentially because drag is a product of Velocity squared in the drag equation. This means that if speed doubles, drag quadruples.
The next type of drag is Profile drag and this specifically deals with drag caused by the frictional resistance of the blades as they travel through the air. This is generally affected by airfoil shape and skin friction. To illustrate this imagine a non-efficient airfoil shaped like a block compared to the typical streamlined airfoil. When airflow impacts the block-shaped airfoil it becomes turbulent and very disturbed as it tries to pass around the airfoil. This turbulent airflow is what causes profile drag. Now consider the streamlined airfoil where air passes more efficiently over it. This type of airfoil creates less drag due to its efficiency. Keep in mind that parasite drag and profile drag are different in that parasite drag applies to total drag of the aircraft while profile drag specifically deals with the airfoil itself. Since the airfoil travels so much faster than the actual aircraft due to its relational velocity, it's drag is varies drastically. Profile drag increases gradually with speed because it's based mostly on shape and skin friction. So profile drag is higher than parasite drag at lower airspeeds but eventually gets surpassed as speed increases.
Lastly there's induced drag. Simply put, induced drag is the result of producing lift. It is higher with higher Angles of Attack (AOA) in the blades because more lift generates greater downward velocities / vortices which increase drag. Think back to my videos on Airflow at a Hover ( • Airflow at a Hover in ... ), Effective Translational Lift ( • Effective Translationa... ), and Aerodynamics of a Takeoff ( • Aerodynamics of a Take... ) videos where it takes more power required to fly the helicopter less than ETL and especially at a stationary Out of Ground Effect (OGE) hover. With these higher AOA's at lower airspeed flight profiles, stronger induced flow and vortices form. These decrease drastically as airspeed increases.
When you combine all 3 types of drag together you get a total drag line. This important to understand because it is what performance planning is based on. Each helicopter operator's manual should break down performance charts you that are specific to that aircraft. It from here you get things like:
Max Endurance / Max Lift to Drag Airspeed: this is the least amount of total drag on the aircraft. This speed has the greatest power margin available and can be used to obtain the max time aloft.
Max Range Airspeed: this is the most distance per unit of fuel or simpler put, the most miles per gallon.
Best Climb Angle Airspeed: the best climb rate for the least amount of forward distance covered. This is helpful when you want to takeoff from a confined area.
Fuel burn rates: you can calculate exact fuel burn for each power setting / flight profile.
It's important to understand drag because it is the foundation for performance charts/ planning. And by understanding more about drag, you have a better grasp on helicopter performance in different flight profiles. More specifically, you understand what you can and cannot affect as a pilot. That wraps up the types of drag in helicopters. Thanks for watching! As always, safe flying!
If you enjoyed the video or have any questions or comments, hit the like button and comment below.
Пікірлер: 58
Just got home after taking the SIFT and got a 68. Opened KZread to relax and this video was still up because I needed a refresher before going in. Couldn't have done it without you, sir. Onward and (hopefully) upward!
New student referred to your channel by my instructor. I immediately understood why. Great 10 minute class worth the time of my life clock. 👍🏻🤙🏻
Simply fabulous Jacob, love the dedication with which u elucidate hard to understand topics, turned to simple to grasp. Thumbs up brother. Stay blessed and keep posting. 👍🏻🙂👍🏻.
Fantastic explanations, I’m very impressed with the quality of your videos.
Thanks again for your efforts and expertise, sir. That explanation makes the charts easier for me to understand.
Thank you my professor couldn't teach a bird to fly so this helps alot
Great videos! I've been studying the last year for my CPL and your explanations have been a big help!
Thanks Jacob, this is helping me out so much. All these videos are great, I appreciate your effort.
These total drags are also adding "load" to the engine, the power that has to overcome these "loads". What is not mentioned is the friction or mechanical drag the engine has to overcome as well. Frictional losses...
Profile drag is what is also called “wetted area.” It is the surface of the profile. Which the wind will strike perpendicular. It is the area which even if the angle of attack of the airfoil is zero and no lift is produced and all induced drag is gone, that area will still resist the wind however slight. No matter how streamlined the designers are successful, there will always be some wetted area which remains.
@Pork-Chopper
2 жыл бұрын
Any surface against the wind, no matter how aerodynamic, will have drag. Try moving a butter knife in a bucket of water sideways, you will feel drag, like an oar in the water. Now move the butter knife in a slicing fashion in the water. It "slices" or moves right through the water with much less resistance, or drag, but there still is some drag, however quite small. Change the angle/pitch of the butter knife n you can experiment.. the Rotor
Just downloaded your ebook and while it is a great product overall, you have mislabeled induced drag (c) and parasite drag (a) on the graph. Really appreciate the concise lessons.
nice video.thanks for sharing
Hey Jacob, your videos are so fuc*ing useful for my ATPL(H) studies for EASA exams. Thank you so much!
Great video!
Excellent!! Thanks Jacob!
Very good Jacob. May I suggest that you light the page from the camera position? This would get rid of the shadow from your writing hand, which often obscures the page.
@helicopterlessonsin10minut10
6 жыл бұрын
Bob Gilchrist. I appreciate the tip. I'm working on improving the lighting setup now. Thanks.
@rigilchrist
6 жыл бұрын
I've been flying helicopters for 30 years but I appreciate your work as it is good to be reminded of the principles!
Brilliant. Thank you.
LOVE THE CHANNEL!
Great video 👌
Thanks Man , good info .
Nice and easy
Thank you so much it makes a lot of sense now
@bakgopiyoyo
Жыл бұрын
Jacob what’s the stall in induced drag?
You really need to get in touch with helicopter online ground school and do videos for them I'm sure they would love to have you on their team.
Good vídeo 👍🏾🚁
Thank you !
How are the calculations of parasitic drag made? My gyroplane is an open air constructed of square tubing and I expect the Wright Brothers machine had better drag numbers than mine does.
@helicopterlessonsin10minut10
4 жыл бұрын
I’m sure it’s determined by either flight or wind tunnel testing and varied by aircraft. Ultimately the engineers who design the aircraft measure it. I don’t have the best answer for you. I fly and teach, but don’t design helicopters.
Induced drag: when the vortices are large/strong/heavy there is a component of force along the direction of vortices that drags the helicopter down or aftwards... _my understanding
What is the drag measurement unit? Is there any?
what are situations where you would want to hang outside of the bucket? are there good weather conditions for example that would motivate you to move right on the x axis if you were in a hurry?
@helicopterlessonsin10minut10
3 жыл бұрын
Take a look at my Crucial Speeds every helicopter pilot should know. Flying Max Range airspeed is the most fuel efficient for distance so it’s the equivalent of best miles per gallon. Also, flying at faster airspeeds may be used as an extra bank account when having to fly lower altitudes. Think, if you have an engine failure you can trade off that inertia to charge the rotor for an autorotation. I outline those principles more in my 3 Bank Accounts video.
Hey Jacob, the book has A and C labeled differently on the graph. I think it’s confusing me a bit.
@jean-louiscavallera4733
4 жыл бұрын
Thanks for some amazing videos and some great explanations. However, i agree with Henry Martinez, I believe there is an error in the book regarding parasite and induced drag. Thanks for all your efforts, and all the best!
Any one can explain how easy identification of faulty flape limiter?
Watching this cause I'm taking my SIFT tomorrow!
muito bom
How are the max range speed or pitch calculated?
@helicopterlessonsin10minut10
3 жыл бұрын
I cover it and more in my Crucial Speeds video. But simply put you divide knots/fuel flow at different speeds to find the highest number.
Does the drag force in the climbing direction matter when the helicopter is climbing?
@helicopterlessonsin10minut10
2 жыл бұрын
I don’t think I understand your question. Can you restate it?
@kuzgun_TR
2 жыл бұрын
@@helicopterlessonsin10minut10 What drag forces occur when climbing?
@helicopterlessonsin10minut10
2 жыл бұрын
You’re still going to have the same types of drag although if you climb there is generally reduced induced flow because the resultant relative wind impacts the rotor different. The reverse is true for descents.
How parasite power varies with increase in altitude ???
@helicopterlessonsin10minut10
2 жыл бұрын
Generally it’s a product of speed. Technically the air gets less dense as you increase altitude so theoretically it wouldn’t increase as quickly at higher altitudes. But this difference would be hard to notice or measure as a pilot.
hi
How parasite power varies with altitude . Can anyone throw some light on this. Regards Ashish
@helicopterlessonsin10minut10
2 жыл бұрын
Generally it’s a product of speed. Technically the air gets less dense as you increase altitude so theoretically it wouldn’t increase as quickly at higher altitudes. But this difference would be hard to notice or measure as a pilot.
@jordanseaman1538
2 жыл бұрын
I agree. Density decreases at higher altitudes which means the helicopter flies through the air easier, but the airfoils (rotors) aren't as efficient, therefore, equalizing. Or on a miniscule level only meant for engineers/scientists to calculate.
Parasite Drag + Profile Drag + Induced Drag = My Ex
A,bcd,eh
W0w! at zero speed the drag FORCE on the helicopter is according to you large! THAT is not possible You are confusing drag with power , mister. Thrust in unaccelerated flight must equal drag. In hover the Helicopter Rotor Thrust in forward direction is zero, so no drag FORCE, Zero. The rotating blades do have drag , creating a moment about the rotor axis, which the engine must overcome. This moment times the angular velocity is the POWER the engine, after friction losses must provide. In Hover, at zero speed with a tail rotor pushing the tail, The Rotor must oppose this lateral tailforce with an equal and opposite tilted rotor side force. That small force is the only force in the plane of the rotor produced. The rotor POWER is the sum of the blade friction (parasite) power and the induced power required to push the air through the rotor to generate the lift that supports the helicopter weight., So far all the foregoing in hover flight. Some simple equations: Induced POWER of the rotor P = L^1.5 × √(2/π rho) ÷ Dia. Dia rotor diameter rho air density L rotor lift force > weight
@arturoeugster7228
Жыл бұрын
Yes, and the parasite rotor power is D = 3/4 Lift Vtip Cd/Cl also a simple equation
stop waffling
@windowsxseven
Жыл бұрын
yeah